Re: [Ocfs2-devel] [PATCH v2 1/5] ocfs2: fix mounting crash if journal is not alloced

[Joseph Qi via Ocfs2-devel <ocfs2-devel@oss.oracle.com>]

On 4/13/22 4:29 PM, Heming Zhao wrote:
> After commit da5e7c87827e8 ("ocfs2: cleanup journal init and shutdown"),
> journal init later than before, it makes NULL pointer access in free
> routine.
> 
> Crash flow:
> 
> ocfs2_fill_super
>  + ocfs2_mount_volume
>  |  + ocfs2_dlm_init //fail & return, osb->journal is NULL.
>  |  + ...
>  |  + ocfs2_check_volume //no chance to init osb->journal
>  |
>  + ...
>  + ocfs2_dismount_volume
>     ocfs2_release_system_inodes
>       ...
>        evict
>         ...
>          ocfs2_clear_inode
>           ocfs2_checkpoint_inode
>            ocfs2_ci_fully_checkpointed
>             time_after(journal->j_trans_id, ci->ci_last_trans)
>              + journal is empty, crash!
> 
> For fixing, there are three solutions:
> 
> 1> Partly revert commit da5e7c87827e8
> 
> For avoiding kernel crash, this make sense for us. We only concerned
> whether there has any non-system inode access before dlm init. The
> answer is NO. And all journal replay/recovery handling happen after
> dlm & journal init done. So this method is not graceful but workable.
> 
> 2> Add osb->journal check in free inode routine (eg ocfs2_clear_inode)
> 
> The fix code is special for mounting phase, but it will continue
> working after mounting stage. In another word, this method adds useless
> code in normal inode free flow.
> 
> 3> Do directly free inode in mounting phase
> 
> This method is brutal/complex and may introduce unsafe code, currently
> maintainer didn't like.
> 
> At last, we chose method <1> and did partly reverted job.
> We reverted journal init codes, and kept cleanup codes flow.
> 
> Fixes: da5e7c87827e8 ("ocfs2: cleanup journal init and shutdown")
> Signed-off-by: Heming Zhao <heming.zhao@suse.com>
> ---
>  fs/ocfs2/inode.c   |  4 ++--
>  fs/ocfs2/journal.c | 32 ++++++++++++++++++++++----------
>  fs/ocfs2/super.c   | 16 ++++++++++++++++
>  3 files changed, 40 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 5739dc301569..bb116c39b581 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -125,6 +125,7 @@ struct inode *ocfs2_iget(struct ocfs2_super *osb, u64 blkno, unsigned flags,
>  	struct inode *inode = NULL;
>  	struct super_block *sb = osb->sb;
>  	struct ocfs2_find_inode_args args;
> +	journal_t *journal = osb->journal->j_journal;
>  
>  	trace_ocfs2_iget_begin((unsigned long long)blkno, flags,
>  			       sysfile_type);
> @@ -171,11 +172,10 @@ struct inode *ocfs2_iget(struct ocfs2_super *osb, u64 blkno, unsigned flags,
>  	 * part of the transaction - the inode could have been reclaimed and
>  	 * now it is reread from disk.
>  	 */
> -	if (osb->journal) {
> +	if (journal) {
>  		transaction_t *transaction;
>  		tid_t tid;
>  		struct ocfs2_inode_info *oi = OCFS2_I(inode);
> -		journal_t *journal = osb->journal->j_journal;
>  
>  		read_lock(&journal->j_state_lock);
>  		if (journal->j_running_transaction)
> diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
> index 1887a2708709..49255fddce45 100644
> --- a/fs/ocfs2/journal.c
> +++ b/fs/ocfs2/journal.c
> @@ -810,22 +810,20 @@ void ocfs2_set_journal_params(struct ocfs2_super *osb)
>  	write_unlock(&journal->j_state_lock);
>  }
>  
> -int ocfs2_journal_init(struct ocfs2_super *osb, int *dirty)
> +/*
> + * alloc & initialize skeleton for journal structure.
> + * ocfs2_journal_init() will make fs have journal ability.
> + */
> +int ocfs2_journal_alloc(struct ocfs2_super *osb)
>  {
> -	int status = -1;
> -	struct inode *inode = NULL; /* the journal inode */
> -	journal_t *j_journal = NULL;
> -	struct ocfs2_journal *journal = NULL;
> -	struct ocfs2_dinode *di = NULL;
> -	struct buffer_head *bh = NULL;
> -	int inode_lock = 0;
> +	int status = 0;
> +	struct ocfs2_journal *journal;
>  
> -	/* initialize our journal structure */
>  	journal = kzalloc(sizeof(struct ocfs2_journal), GFP_KERNEL);
>  	if (!journal) {
>  		mlog(ML_ERROR, "unable to alloc journal\n");
>  		status = -ENOMEM;
> -		goto done;
> +		goto bail;
>  	}
>  	osb->journal = journal;
>  	journal->j_osb = osb;
> @@ -839,6 +837,20 @@ int ocfs2_journal_init(struct ocfs2_super *osb, int *dirty)
>  	INIT_WORK(&journal->j_recovery_work, ocfs2_complete_recovery);
>  	journal->j_state = OCFS2_JOURNAL_FREE;
>  
> +bail:
> +	return status;
> +}
> +
> +int ocfs2_journal_init(struct ocfs2_super *osb, int *dirty)
> +{
> +	int status = -1;
> +	struct inode *inode = NULL; /* the journal inode */
> +	journal_t *j_journal = NULL;
> +	struct ocfs2_journal *journal = osb->journal;
> +	struct ocfs2_dinode *di = NULL;
> +	struct buffer_head *bh = NULL;
> +	int inode_lock = 0;
> +

Better to leave a BUG_ON(!journal) here like before.

>  	/* already have the inode for our journal */
>  	inode = ocfs2_get_system_file_inode(osb, JOURNAL_SYSTEM_INODE,
>  					    osb->slot_num);
> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
> index 477cdf94122e..babec2c9d638 100644
> --- a/fs/ocfs2/super.c
> +++ b/fs/ocfs2/super.c
> @@ -2015,6 +2015,7 @@ static int ocfs2_initialize_super(struct super_block *sb,
>  	int i, cbits, bbits;
>  	struct ocfs2_dinode *di = (struct ocfs2_dinode *)bh->b_data;
>  	struct inode *inode = NULL;
> +	struct ocfs2_journal *journal;
>  	struct ocfs2_super *osb;
>  	u64 total_blocks;
>  
> @@ -2195,6 +2196,15 @@ static int ocfs2_initialize_super(struct super_block *sb,
>  
>  	get_random_bytes(&osb->s_next_generation, sizeof(u32));
>  
> +	/*
> +	 * FIXME
> +	 * This should be done in ocfs2_journal_init(), but any inode
> +	 * writes back operation will cause the filesystem to crash.
> +	 */
> +	status = ocfs2_journal_alloc(osb);
> +	if (status)

Explicitly mark 'status < 0'?

Thanks,
Joseph

> +		goto bail;
> +
>  	INIT_WORK(&osb->dquot_drop_work, ocfs2_drop_dquot_refs);
>  	init_llist_head(&osb->dquot_drop_list);
>  
> @@ -2483,6 +2493,12 @@ static void ocfs2_delete_osb(struct ocfs2_super *osb)
>  
>  	kfree(osb->osb_orphan_wipes);
>  	kfree(osb->slot_recovery_generations);
> +	/* FIXME
> +	 * This belongs in journal shutdown, but because we have to
> +	 * allocate osb->journal at the middle of ocfs2_initialize_super(),
> +	 * we free it here.
> +	 */
> +	kfree(osb->journal);
>  	kfree(osb->local_alloc_copy);
>  	kfree(osb->uuid_str);
>  	kfree(osb->vol_label);

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